Already known for use in supercritical refrigeration cycles is a heat exchanger comprising a pair of header tanks arranged as spaced apart from each other, heat exchange tubes arranged in parallel at a spacing between the pair of headers and having opposite ends joined to the respective headers, and fins arranged in respective air passing clearances between respective adjacent pairs of heat exchange tubes and each joined to the tubes adjacent thereto, each of the header tanks comprising a header member in the form of a major arc in cross section, a pipe connecting plate having tube inserting slits extending through the thickness thereof and arranged longitudinally thereof at a spacing, the connecting plate being in the form of a minor arc in cross section for closing a longitudinal opening of the header member, an intermediate plate disposed inwardly of the tube connecting plate and extending therealong, the intermediate plate having a plurality of communication holes extending therethrough and arranged longitudinally thereof at a spacing for holding the respective tube inserting slits in communication with the interior of the header member therethrough, and caps closing respective opposite end openings (see the publication of JP-A No. 2001-133189, FIGS. 1 to 5).
However, the header tank included in the heat exchanger of the publication requires caps for closing opposite end openings and therefore has the problem of necessitating an increased number of components and being low in the efficiency of work for joining the caps to the header member, pipe connecting plate and intermediate plate. Additionally, the caps must be made as separate members and are cumbersome to make.
To improve the heat exchanger disclosed in the publication in heat exchange performance, it is desirable to change the course of flow of the refrigerant, for example, by dividing the interior of at least one of the header tanks with a partition, whereas this entails the problem that the provision of the partition requires a cumbersome procedure.
An object of the present invention is to overcome the above problems and to provide a heat exchanger header tank which is smaller in the number of components, can be fabricated by more efficient work and is capable of giving a higher heat exchange efficiency to heat exchangers than the conventional heat exchanger header tank, and a heat exchanger comprising the header tank.